/Engine/Source/Editor/UnrealEd/Public/EditorLevelUtils.h
Adds the named level package to the world. Does nothing if the level already exists in the world.
The new level, or NULL if the level couldn't added.
static [ULevelStreaming](API\Runtime\Engine\Engine\ULevelStreaming) * AddLevelToWorld ( [UWorld](API\Runtime\Engine\Engine\UWorld) * InWorld, const TCHAR * LevelPackageName, [TSubclassOf](API\Runtime\CoreUObject\Templates\TSubclassOf)< [ULevelStreaming](API\Runtime\Engine\Engine\ULevelStreaming) > LevelStreamingClass, const FTransform & LevelTransform )